The invention relates to a surface covering. More particularly, the invention relates to a surface covering having an inorganic wear layer which preferably has been deposited on a support structure by a low pressure environment deposition technique.
Floor coverings having wear layers are well known in the art. Such wear layers protect the decorative layer of the floor coverings and lengthen the useful life of the floor covering. With the exception of ceramic tile which are rigid and must typically be installed on a mortar bed and metal floors such as steel plates, neither of which have a wear layer per se, inorganic material is not used as the wear surface of floor coverings. Inorganic materials are typically considered too brittle to be walked on; particularly if a "thin" layer were to be placed over a flexible or conformable support layer. Further, low pressure environment deposition techniques have not been applied to the manufacture of floor coverings.
Reduced pressure environment techniques for depositing films of hard inorganic materials include sputtering, plasma polymerization, physical vapor deposition, chemical vapor deposition, ion plating and ion implantation. Hard inorganic materials which can be prepared using these techniques include metals, metal oxides, metal nitrides and mixtures thereof; such as aluminum oxide, silicon oxide, tin and/or indium oxide, titanium dioxide, zirconium dioxide, tantalum oxide, chromium oxide, aluminum nitride, boron nitride, silicon nitride, titanium nitride, and zirconium nitride.
Often the partial pressures of key gases in the deposition environment are controlled to effect the properties and compositions of the deposited material. Therefore, a film formed on a substrate by reactive sputtering or reactive deposition can be a compound derived from a metal and a controlling gas, i.e., aluminum oxide produced by sputtering aluminum in oxygen. Sometimes the controlling gases are used to sustain a plasma in the deposition environment. Ion assisted deposition is a technique in which the controlled gas is ionized and is used to bombard the deposition surface to modify the morphology and physical properties of the resulting film.
A critical review of vapor deposition technology related to hard coatings was presented by J. E. Sundgren and H. T. C. Hentzell in J. Vac. Sci. Tech. A4(5), September/October 1987, 2259-2279. A more complete review of techniques involved in formation of thin films in reduced pressure environments is the book edited by J. L. Vossen and W. Kern, Thin Film Processes, Academic, New York, 1978.
Recent articles on thin film preparation include Clevenger, L. A., Thompson, C. V. and Cammarata, R. C., Appl. Phys. Letter, 52(10), 7 March 1988, 795-797 on using commercial photoresists as supports; and Journal of Materials Science Letters, (1986), 177-178.
Patents dealing with thin film deposition include: U.S. Pat. Nos. 4,604,181 and 4,702,963.
Reduced pressure environment techniques have been used to coat plastics materials such as plastic bags to improve gas impermeability. However, such coatings have been limited to about 0.5 microns in thickness.
While reduced pressure environment techniques have been used to form hard coatings on surfaces such as automobile parts, there has been no suggestion that such coatings could be successfully used as wear surfaces for floor coverings. In fact, such coatings tend to be brittle when applied in a substantial thickness. Thus, one skilled in the flooring art would not expect reduced pressure environment deposited materials to function adequately as a floor covering or on other support surfaces which are flexible, particularly in the thickness deemed necessary to protect the decorative layer of a floor covering.
Alliance Wall manufactures and sells wall coverings in which porcelain enamel is fused to a steel sheet. However, use of a material as a wall covering does not suggest that it would be acceptable as a floor covering. Again, one skilled in the flooring art would not expect a thin sheet of ceramic to withstand the long term abuse to which flooring is subjected, particularly when laid over a resilient support structure and walked on by a woman in high heels.
Further, while reduced pressure environment techniques have been used to prepare protective coatings on plastics, the thickness of the prior art protective coatings generally do not exceed 0.5 microns. Typically this is because the deposition of hard coatings at greater thicknesses causes the temperature to exceed the allowable use temperature of the support. In addition, it is widely believed that although a hard inorganic coating on a polymer would provide some protection function, the brittleness associated with hard materials usually is believed to be a severe limitation. In fact, we have found that the brittleness is not a limitation, and have prepared materials that function superbly as protective coatings on organic layers or substrates.